Some types of oat cereals, oatmeal, granola and snack bars contain higher levels of a chemical found in the weed killer Roundup than what the Environmental Working Group considers safe, according to a report released Wednesday by the advocacy group.

Almost three-quarters of food samples tested showed higher glyphosate levels than what the group’s scientists believe to be “protective of children’s health,” the report indicates.

Last week, a jury at the Superior Court of California in San Francisco awarded $289 million in damages to a groundskeeper whose attorney argued that Roundup, a weed killer made by Monsanto, caused his terminal cancer.

“We will appeal this decision and continue to vigorously defend this product, which has a 40-year history of safe use and continues to be a vital, effective and safe tool for farmers and others,” Monsanto Vice President Scott Partridge said in a statement at the time.

“More than 800 scientific studies, the US EPA, the National Institutes of Health and regulators around the world have concluded that glyphosate is safe for use and does not cause cancer,” Partridge said.

However, the human health effects of glyphosate remain uncertain, because the product has additional chemical ingredients that, individually or combined, might be carcinogenic, among other reasons. Many scientists and scientific organizations, including the US Environmental Protection Agency, state that in the amounts commonly consumed in food, glyphosate is not harmful to human health.

However, the International Agency for Research on Cancer, the cancer agency that falls under the World Health Organization, classifies it as “probably carcinogenic to humans.”

“Not every health agency in the world and not every spokesperson in the world has agreed that glyphosate can cause cancer,” said Olga Naidenko, the Environmental Working Group’s senior science adviser for children’s health.

However, Naidenko, who was not an author of the report, believes that there are “conflicts of interest standing behind some” of the positive opinions of glyphosate and that Monsanto has tried to influence the EPA so that it will continue to allow use of the chemical in the United States.

Over 750 herbicideproducts containing glyphosate are for sale in the United States, according to the National Pesticide Information Center, a cooperative formed by Oregon State University and the EPA.

A ‘more protective’ guideline

Introduced to the American market in 1974, glyphosate is an herbicide that can kill both broadleaf plants and grasses. Glyphosate products are used on farms, industrial areas, public parks, residential lawns and gardens, and aquatic systems for agricultural and forestry purposes.

For its new report, the Environmental Working Group conducted toxicology tests on dozens of oat-based foods sold across the country and used a health benchmark for glyphosate based on a cancer risk assessment that was developed by California state scientists, explained Alexis Temkin, author of the report and the group’s toxicologist.

“EWG used that level to then develop a guideline that was more protective for children’s health,” Temkin said. “It’s 100-fold lower.”

The Environmental Working Group’s guideline amount is 0.01 milligram per day, Naidenko said. Should this small amount be present in a single portion of food — about 2 ounces, 60 grams or roughly two cups of cereal — that would amount to a concentration of 160 parts per billion.

In other words, the group says that a person eating two cups of cereal a day contaminated by 160 parts of glyphosate per billion would have a one in a million risk of cancer linked to the chemical, according to Naidenko.

Of 45 samples of food products made with conventionally grown oats, two had no detectable glyphosate, 12 had levels of glyphosate that were lower than the group’s acceptable health benchmark, and 31 had levels of glyphosate at or higher than the benchmark. The highest levels were detected in two samples of Quaker Old Fashioned Oats.

“Quaker does not add glyphosate during any part of the milling process,” the company said in a statement. “Glyphosate is commonly used by farmers across the industry who apply it pre-harvest. Once the oats are transported to us, we put them through our rigorous process that thoroughly cleanses them (de-hulled, cleaned, roasted and flaked). Any levels of glyphosate that may remain are significantly below any limits and well within compliance of the safety standards set by the Environmental Protection Agency (EPA) and the European Commission as safe for human consumption.”

In the tests, glyphosate was also found at detectable concentrations in five of 16 organic oat food samples.

The Environmental Working Group is focused on lifetime exposure to toxic herbicides, Naidenko said.

Conflicting results

“The concern about glyphosate is for long-term exposure,” she said. “As most health agencies would say, a single portion would not cause deleterious effects. But think about eating popular foods such as oatmeal every day or almost every day — that’s when, according to scientific assessments, such amounts of glyphosate might pose health harm.”

Glyphosate does not easily pass through human skin, and when it is ingested, it passes through the body relatively quickly, according to the National Pesticide Information Center. The vast majority of glyphosate leaves the body in urine and feces without being changed into another chemical. In some studies, high doses given to laboratory animals suggests this chemical has carcinogenic potential.

“Studies on cancer rates in people have provided conflicting results on whether the use of glyphosate containing products is associated with cancer,” the center’s website states. “Some studies have associated glyphosate use with non-Hodgkin lymphoma.”

Temkin said “That’s correct that glyphosate is metabolized very quickly and eliminated in the urine,” adding that other types of chemicals are metabolized very quickly yet are known to cause some harm. “Arguments that quick metabolism cannot result in harm from exposure to a chemical — especially if it’s a chemical that is very ubiquitous and something that somebody is exposed to on a daily basis — does not mean that it can’t have health effects.”

The glyphosate debate continues

But Alex Berezow, senior fellow of biomedical science at the American Council on Science and Health, a nonprofit group that says it advocates for evidence-based science and medicine,believes the new report is “absolutely atrocious.”

“The good news is that nobody on Earth consumes anywhere near that amount of glyphosate,” said Berezow. “The EWG fabricated its own safety standard so that they could promote organic food. They’ve been doing this for years — ignoring the scientific literature in order to lobby for the organic industry.”

Berezow said the chemical is “completely safe” to humans because it interferes with chemical reactions in plants that do not exist in humans. Because we lack this “metabolic pathway,” he said, “it’s not even hypothetically possible for glyphosate to be harmful.”

Dr. Paul Pharoah, professor of cancer epidemiology at the University of Cambridge, wrote in an email that “there have been multiple studies investigating the potential association between glyphosate exposure and cancer risk.”

“Some of these studies have serious flaws in their design,” said Pharoah, who was not involved in the new report. “It is not scientifically possible to prove ‘no association,’ but the evidence from these studies is that if there is an association the effect is very small.”

Pharoah said he could not comment on the methods used by the Environmental Working Group or the accuracy of the results, since he is an epidemiologist and not a toxicologist.

Still, he said he would not be “unduly concerned” about the health risks to children, given the lack of evidence linking the chemical to cancer in adults.

“This is not to say that I do not think that public policy should limit the acceptable amount of these chemicals found in foods,” Pharoah said.

“This kind of chemical dependency is just not going to go overnight,” she said. “We know it is possible to grow oats and other grains without herbicides. Companies do not need to wait for EPA; they can simply talk to their suppliers and say, ‘please grow our oats without glyphosate, because our customers are complaining.’ ”

Temkin added, “this type of use of glyphosate is a very small percentage of the overall use, yet it can have the greatest impact on human health, so we think this is the place to target reducing the use of glyphosate.

“What we do know is that people don’t want to have pesticides or herbicides in their foods, and families really shouldn’t have to make a healthy choice that also comes with an additional risk,” she said.